Among patients presenting to emergency departments with abdominal pain, the underlying causes of the pain range from benign processes to acute, life-threatening disease. The most common abdominal operation performed on an emergency basis is the appendectomy, which is performed more than 250,000 times annually in the United States. Using a hypothetic illustrative case, Paulson and colleagues review the management of patients with suspected appendicitis.

A previously healthy 22-year-old woman presents to the emergency department with acute abdominal pain in the right lower quadrant of 18 hours' duration. She has no fever, and her examination is remarkable only for right lower quadrant tenderness without peritoneal signs.

The authors first discuss the aspects of the history and physical examination that may be used to develop a clinical suspicion of acute appendicitis. The sensitivity and specificity of various signs and symptoms relating to appendicitis are reviewed in the accompanying table. The three factors with the highest predictive value for acute appendicitis are right lower quadrant pain, abdominal rigidity, and migration of pain from the periumbilical region to the right lower quadrant. A shorter duration of pain also supports the diagnosis of appendicitis, whereas other causes of abdominal pain may have a shorter course of pain.

Laboratory studies in patients with abdominal pain share the limited sensitivity and specificity of the history and physical examination. Pregnancy must always be ruled out in women of reproductive age. An elevated leukocyte count is usually noted in cases of acute appendicitis, but it has poor specificity. While urinalysis will often show some pyuria, hematuria, or bacteriuria in patients with appendicitis, more than 20 leukocytes per high-power field or more than 30 red cells per high-power field is suggestive of a urinary tract disorder.

In equivocal cases, the authors note that observation of patients for six to 10 hours has been shown to decrease the number of unnecessary surgeries without increasing the rate of appendiceal perforation.

Imaging is also commonly involved in cases with an unclear diagnosis. In the authors' opinion, plain abdominal radiographs and contrast barium-enema examinations have little clinical utility. Abdominal ultrasonography may be useful in ruling out appendicitis; however, because the appendix is usually not well visualized, the physician is left uncertain of the diagnosis. Computed tomographic (CT) scanning has improved with the advent of rapid-scanning spiral CT machines, which decrease image artifact caused by movement. A retrospective review of 650 patients with suspected appendicitis showed a sensitivity of 97 percent and a specificity of 98 percent with spiral CT. In patients in which the clinical suspicion was uncertain, sensitivity was 92 percent and specificity was 85 percent.

Two prospective studies comparing ultrasonography with spiral CT have favored the latter modality. Cost-effectiveness studies have also supported the utility of CT scans, especially in female patients, because of the decreased accuracy of the clinical examination in correctly predicting appendicitis.